Minor Postgresql Downgrade

similar like minor postgresql downgrade, it's also respect the primaryUpdateStrategy & primaryUpdateStrategy.

1. downgrade the cluster

   kubectl apply -f cluster.yaml
   
   apiVersion: postgresql.cnpg.io/v1
   kind: Cluster
   metadata:
     name: echo-postgresql-upgrade-test
     namespace: cnpg-system
   spec:
     imageName: ghcr.io/cloudnative-pg/postgresql:17.0
     instances: 2
     storage:
       size: 1Gi
     primaryUpdateStrategy: supervised
   

2. since this is supervised. replica will be automatically downgraded, and wait manual intervention to delete master pod or switchover

   zufar.dhiyaullhaq@MacBookPro 5-minor-postgresql-downgrade % k get cluster
   NAME                           AGE     INSTANCES   READY   STATUS                     PRIMARY
   echo-postgresql-upgrade-test   4h53m   2           2       Waiting for user action    echo-postgresql-upgrade-test-1
   
   echo-postgresql-upgrade-test-1             1/1     Running   0          12m
   echo-postgresql-upgrade-test-2             1/1     Running   0          4m8s
   
   zufar.dhiyaullhaq@MacBookPro 5-minor-postgresql-downgrade % k get pod echo-postgresql-upgrade-test-2 -oyaml | grep image
       image: ghcr.io/cloudnative-pg/postgresql:17.0
   
   zufar.dhiyaullhaq@MacBookPro 5-minor-postgresql-downgrade % k get pod echo-postgresql-upgrade-test-1 -oyaml | grep image
       image: ghcr.io/cloudnative-pg/postgresql:17.5
   

3. switchover the master, there will be downtime for 5-10s

   kubectl cnpg promote echo-postgresql-upgrade-test echo-postgresql-upgrade-test-2
   
   zufar.dhiyaullhaq@MacBookPro 5-minor-postgresql-downgrade % k get cluster                                                                   
   NAME                           AGE     INSTANCES   READY   STATUS                     PRIMARY
   echo-postgresql                8d      5           5       Cluster in healthy state   echo-postgresql-8
   echo-postgresql-upgrade-test   4h55m   2           1       Switchover in progress     echo-postgresql-upgrade-test-2
   
   zufar.dhiyaullhaq@MacBookPro 5-minor-postgresql-downgrade % k get pod echo-postgresql-upgrade-test-2 -oyaml | grep image
       image: ghcr.io/cloudnative-pg/postgresql:17.0
   
   zufar.dhiyaullhaq@MacBookPro 5-minor-postgresql-downgrade % k get pod echo-postgresql-upgrade-test-1 -oyaml | grep image
       image: ghcr.io/cloudnative-pg/postgresql:17.0
   

Manifests

cluster.yaml

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: echo-postgresql-upgrade-test
  namespace: cnpg-system
spec:
  imageName: ghcr.io/cloudnative-pg/postgresql:17.0
  instances: 2
  storage:
    size: 1Gi
    storageClass: gtf-ack-essd-pl0-wait
  ## supervised upgrade strategy ##
  primaryUpdateStrategy: supervised
  ## unsupervised upgrade strategy ##
  # primaryUpdateStrategy: unsupervised
  # primaryUpdateMethod: switchover

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: echo-postgresql-upgrade
  namespace: cnpg-system
  labels:
    app: echo-postgresql-upgrade
spec:
  replicas: 1
  selector:
    matchLabels:
      app: echo-postgresql-upgrade
  template:
    metadata:
      labels:
        app: echo-postgresql-upgrade
    spec:
      containers:
      - name: echo-postgresql-upgrade
        image: ghcr.io/zufardhiyaulhaq/echo-postgresql:v1.0.0
        ports:
        - containerPort: 8080
          name: http
        env:
        - name: HTTP_PORT
          value: "8080"
        - name: POSTGRESQL_HOST
          value: "echo-postgresql-upgrade-test-rw.cnpg-system.svc.cluster.local"
        - name: POSTGRESQL_PORT
          value: "5432"
        - name: POSTGRESQL_DATABASE
          valueFrom:
            secretKeyRef:
              name: echo-postgresql-upgrade-test-app
              key: dbname
        - name: POSTGRESQL_USER
          valueFrom:
            secretKeyRef:
              name: echo-postgresql-upgrade-test-app
              key: user
        - name: POSTGRESQL_PASSWORD
          valueFrom:
            secretKeyRef:
              name: echo-postgresql-upgrade-test-app
              key: password
        resources:
          requests:
            cpu: "100m"
            memory: "128Mi"
          limits:
            cpu: "500m"
            memory: "512Mi"
---
apiVersion: v1
kind: Service
metadata:
  name: echo-postgresql-upgrade
  namespace: cnpg-system
spec:
  selector:
    app: echo-postgresql-upgrade
  ports:
    - protocol: TCP
      port: 8080
      targetPort: http
  type: ClusterIP